<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
      #d1{
        width: 200px;
        height: 200px;
        border: 10px double red;
        /*设置圆角:值越大越圆,超过宽高的一半时为正圆*/
        border-radius: 110px;
      }
      #d2{
        width: 300px;
        height: 300px;
        border: 1px solid blue;

        /*默认情况下给元素添加内边距会影响元素的宽高*/
        padding-top: 200px;
        padding-left: 200px;
        /*添加此样式后内边距将不再影响元素的宽高*/
        box-sizing: border-box;
      }
    </style>
</head>
<body>
<div id="d1">边框测试</div>
<div id="d2">内边距测试</div>
</body>
</html>